1. Field of the Invention
The present invention relates to a recordable and reproducible disk having a sector structure and a disk recording and reproducing apparatus, and more specifically to a method for managing a defect of a disk susceptible to a scratch and an apparatus for recording information onto and reproducing information from the disk.
2. Description of the Related Art
A representative example of a disk having a sector structure includes an optical disk. In recent years, capacity of optical disks has been remarkably increased, and data has been recorded on an optical disk in high density. Therefore, it is important to ensure reliability when information is recorded onto an optical disk or when information is reproduced from an optical disk.
FIGS. 1A through 1C show a general physical and logical structure of a disk medium 1.
FIG. 1A is a schematic diagram of the disk medium 1. The disk medium 1 in a circular shape includes a plurality of concentrically formed tracks 2. Each track 2 is divided into a plurality of sectors 3 in a radius direction. A leading edge of each sector 3 is provided with an absolute address called a physical sector address. Herein, the "leading edge" refers to an edge of each sector 3 in a rotation direction in which the disk medium 1 is rotated.
FIG. 1B schematically shows a sector management method. Tracks are assigned numbers (0 to T). Sectors included in each track are assigned numbers (0 to S). Each sector can be accessed by specifying a track number and a sector number.
FIG. 1C shows a structure of areas of the disk medium 1 (FIG. 1A). The disk medium 1 (FIG. 1A) is composed of a disk information area 4 and a data recording area 5. The disk information area 4 is positioned on an innermost side and on an outermost side of the disk medium 1 (FIG. 1A). In the disk information area 4, parameters and the like required for accessing a disk are stored. The data recording area 5 is positioned between the disk information areas 4 on an innermost side and on an outermost side. In the data recording area 5, ordinary data such as video data and audio data is stored. For recording and reproducing data, a disk is initialized, and data is written onto the data recording area 5.
In recording of information onto and reproduction of information from an optical disk, the procedure described below is used for ensuring reliability. More specifically, in the case where there is a sector on a disk in which information cannot be recorded or reproduced, the sector is registered as a defective sector, and the use of the defective sector is prohibited. The procedure will be described in accordance with International Standardization Organization ISO/IEC10090.
In the case where a defect is found in a sector during recording and reproduction of data, the sector is registered as a defective sector in a Primary Defect List (hereinafter, referred to as a "PDL") and/or in a Secondary Defect List (hereinafter, referred to as an "SDL"). Herein, the "defect" refers to the case where there is a physical scratch in a sector in a track. A disk recording and reproducing apparatus does not use the defective sector registered in the PDL or the SDL in the subsequent recording and reproduction, thereby being capable of recording and reproducing data without accessing the defective sector. The PDL and the SDL are stored in the disk information area 4 in FIG. 1C.
FIG. 10A shows a structure of the PDL. The PDL is composed of a PDL identifier identifying the PDL, the number of entries showing the number of defective sectors registered in the PDL, and n entries (PDE1 to PDEn) storing addresses of actual defective sectors.
FIG. 10B shows a structure of the PDEn. The PDEn stores an address of a defective sector specified by a track number and a sector number. The PDE1 to PDE(n-1) also have the same structure as that of the PDEn.
FIG. 11A shows a structure of the SDL. In the same way as in the PDL, the SDL is composed of an SDL identifier identifying the SDL, the number of entries showing the number of defective sectors registered in the SDL, and m entries (SDE1 to SDEm) storing addresses of actual defective sectors.
FIG. 11B shows a structure of the SDEm. The SDEm stores a defective sector address and an alternative sector address thereof. The defective sector address and the alternative sector address are both specified by a track number and a sector number. The SDE1 to SDE(m-1) also have the same structure as that of the SDEm. The difference between the PDL and the SDL is that the SDL has an alternative sector address.
Next, two algorithms for avoiding a defective sector, i.e., a Slipping Algorithm and a Linear Replacement Algorithm will be described.
FIG. 12 shows a defective sector and an alternative sector thereof to which the Slipping Algorithm is applied. The Slipping Algorithm is a defect handling algorithm conducted during disk inspection and formatting.
A user area and a spare area of a schematic area 1201 shown in FIG. 12 are formed as part of the data recording area 5 (FIG. 1C). The user area is provided for the purpose of actually storing data, and data is usually stored in this area. The spare area is provided for the purpose of handling a defective sector. More specifically, the spare area is provided considering that there may be a defective sector in the user area in which data cannot be stored due to a scratch or the like.
In order to access the user area, a disk is assigned a logical sector number (hereinafter, referred to as an "LSN"). A user or an external terminal controlling a disk recording and reproducing apparatus accesses a sector of a disk, using an LSN, and reads and writes data.
A logical area 1202 shown in FIG. 12 shows results obtained by handling a defective sector by the Slipping Algorithm. It is assumed that a defective sector SD1 having one sector of defect and a defective sector SD2 having two sectors of defect are present in the user area. The defective sectors SD1 and SD2 are not assigned LSNs, and three sectors which cannot be used due to defects are reserved by using the spare area. As a result, the user area formally extends to the spare area as shown in FIG. 12, and an area with the same capacity as that which can be used without any defects is reserved.
Thus, in accordance with the Slipping Algorithm, the use of an address of a defective sector registered in the PDL can be avoided. Furthermore, by prescribing the spare area as an alternative area of a defective sector, a required recording area can be reserved.
FIG. 13 shows defective sectors and alternative sectors thereof to which the Linear Replacement Algorithm is applied. The Linear Replacement Algorithm is a defect handling algorithm generally conducted during recording and reproduction of data.
In FIG. 13, it is assumed that defective sectors LD1 and LD2 are present in the user area. Data of the defective sectors LD1 and LD2 is reserved in a selectively specified area of the spare area. According to the Linear Replacement Algorithm, LSNs (e.g., LSN1 and LSN3) assigned to sectors before and after a defective sector refer to the sectors before and after the defective sector, and LSN2 between LSN1 and LSN3 refers to an alternative sector in the spare area.
Thus, according to the Linear Replacement Algorithm, a defective sector is registered in the SDL, and an alternative sector is accessed in place of the defective sector; thus, the alternative sector is used as an alternative to the defective sector.
Hereinafter, a procedure of disk initialization will be described.
Initialization of a disk is performed at least once before data is written onto the disk. The procedure of initialization is as follows. First, specific test pattern data is written onto all the sectors, and the sectors of the disk are inspected based on whether or not the written data can be correctly read from all the sectors.
As described above, a defective sector from which data cannot be read during the inspection in the course of disk initialization is handled as a defective sector by the Slipping Algorithm which generally performs PDL registration.
FIG. 14 shows a procedure of disk initialization.
When a recording and reproducing apparatus (not shown) starts initialization of a disk, the recording and reproducing apparatus sets an address of a leading edge of a sector to be initialized as an address initial setting value, and writes prepared test data onto the address of the leading edge. Thereafter, error determination E1 is performed. In the error determination E1, it is determined whether or not a sector address is normally read. The reason for this is that a sector address is required to be read first when data is written onto a sector, and in the case where an error occurs in reading the sector address, data cannot be written in the sector address.
When an address read error is detected in the error determination E1, a sector having an error is determined as a defective sector, and the sector address thereof is registered in a first list.
Next, a value of the sector address is increased by one, and test data is written. Thereafter, the error determination E1 is performed again. An address of a sector which is determined to be defective is registered in the first list. This operation is repeated until the final sector address is reached. Then, the leading address value is set as an address initial setting value, and data written onto the leading sector is read.
When data is read, error determination E2 is performed. In the error determination E2, it is determined whether or not read data is correct (i.e., data is successfully written). In the case where an error is detected in read data, a sector having an error is determined as a defective sector, and the sector address thereof is registered in a second list.
Next, a value of the sector address is increased by one, and data is read. Thereafter, the error determination E2 is performed again. An address of a sector which is determined to be defective is registered in the second list. This operation is repeated until the final sector address is reached. When registration in the second list is completed, the first list previously formed and the second list in which registration is completed are combined into one. At this time, the defective sector addresses registered in the combined list are sorted in the order of a sector address, and duplicate registered defective sectors are integrated into one, whereby a PDL as described above is formed. The PDL is stored in the disk information area 4 (FIG. 1C) of a disk.
FIG. 15A shows a position of a defective sector on the disk medium 1 (FIG. 1), and FIG. 15B shows the PDL in which the defective sector is registered.
More specifically, FIG. 15A shows that, for example, a sector at an address (track 0011, sector 02) of the disk is a defective sector. FIG. 15B shows an example of the PDL in which the address of the defective sector is registered as a track number and a sector number.
In the above-mentioned example, a sector at an address (track 0011, sector 02) is registered as a defective sector which cannot be accessed. It can be considered that in order to reserve a recording area corresponding to capacity of the defective sector on which data cannot be recorded, the user area extends to the address (track 0100, sector 00) of the spare area (FIGS. 12 and 13) and is administered by an LSN. At this time, an address (track number and sector number) of the defective sector is recorded in the PDL. Thus, in the case where this defective sector is accessed, the address (track 0011, sector 02) can be skipped.
Next, an operation during recording will be described.
An operation of recording data refers to an operation of writing specified data onto a specified sector. In an operation of recording data, a defective sector on which data cannot be written is handled as a defective sector in accordance with the Linear Replacement Algorithm which generally performs SDL registration.
FIG. 16 shows a procedure of recording data onto a disk.
A general recording and reproducing apparatus sets an address of a leading edge of a sector onto which data is recorded as an address initial setting value, and writes specified data from the leading edge of the addressed sector. Then, the recording and reproducing apparatus performs a verifying process for confirming the success of the write step. The verifying process refers to a process in which data is read from a sector for the purpose of confirming write of data.
After the data is read in the verifying process, it is determined in error determination E3 whether or not the data has been read and whether or not the read data is the same as the specified written data. In the case where the data cannot be read or the read data is different from the specified written data, an error is detected. In the case where the data is read and the read data is the same as the specified written data, an error is not detected. In the case where an error is detected in the read data, the sector which is being verified is determined as a defective sector, and an alternative sector is assigned to the defective sector based on the SDL. The specified data is written onto the alternative sector, and thereafter, the address of the sector determined as a defective sector which is being verified and the address of the alternative sector are registered in the SDL. In the case where an error is not detected in the error determination E3, the sector address is set to be a specified address. Write of data, the verifying process, and the error determination E3 are performed.
This operation is repeated, and after the specified final sector address is reached, the procedure is completed.
FIG. 17A shows positions of a defective sector and an alternative sector thereof on the disk medium 1 (FIG. 1), and FIG. 17B shows the SDL in which the defective sector and the alternative sector thereof are registered.
More specifically, FIG. 17A shows that, for example, a sector at an address (track 0012, sector 04) is a defective sector, and an alternative sector thereof is at an address (track 0100, sector 00). FIG. 17B shows an example of the SDL in which the addresses of the defective sector and the alternative sector thereof are registered by a track number and a sector number.
In the above example, a sector at an address (track 0012, sector 04) is registered as a defective sector which cannot be accessed. As an alternative sector of the defective sector at the address (track 0012, sector 04), a sector at an address (track 0100, sector 00) of the spare area is assigned. At this time, the addresses (track number and sector number) of the defective sector and the alternative sector are registered in the SDL. Thus, in the case where the address (track 0012, sector 04) is accessed, this address is skipped to the address (track 0100, sector 00), and data can be read from the sector at the address (track 0100, sector 00).
Two examples in which either one of the PDL or the SLD is utilized have been described. However, in actual recording and reproduction, both of the PDL and the SDL are generally used.
When a disk is used, disk initialization called formatting is performed only once in the beginning. A defective sector detected during formatting is registered in the PDL. A defective sector detected during recording of data onto a disk after disk initialization is registered in the SDL.
FIGS. 18A through 18C show positions of defective sectors and an alternative sector thereof on the disk medium 1 (FIG. 1), and the PDL and the SDL in which the defective sectors and the alternative sector are registered.
FIG. 18A shows positions of defective sectors and an alternative sector thereof on the disk medium 1 (FIG. 1). FIG. 18A shows that defective sectors SD3 and LD3 are at disk addresses (track 0011, sector 01) and (track 0010, sector 05), and a sector at an address (track 0100, sector 01) is an alternative sector of the defective sector LD3.
FIG. 18B shows the PDL in which the defective sector is registered.
FIG. 18C shows the SDL in which the defective sector and the alternative sector are registered.
A procedure in which the PDL and the SDL shown in FIGS. 18B and 18C is as described below.
First, in the disk initialization (FIG. 14), the sector SD3 at the address (track 0011, sector 01) is registered in the PDL as a defective sector. At this time, the Slipping Algorithm utilizing the PDL is used. An LSN is assigned to the sector of a spare area at the address (track 0100, sector 00), and the sector of the spare area is used as an extended area of a user area.
When the sector LD3 at the address (track 0010, sector 05) is determined to be defective in the recording of data onto a disk (FIG. 16), a sector at an address (track 0100, sector 01) of the spare area is assigned as the alternative sector of the sector LD3. Then, the addresses of the defective sector LD3 and the alternative sector thereof in the spare area are registered in the SDL.
Herein, it will be described that the alternative sector of the defective sector LD3 registered in the SDL is at an address (track 0100, sector 01). Since the number of entries registered in the PDL is one in the defect handling during the previously performed disk initialization, it is understood that an LSN is assigned to one sector from the leading edge of the spare area, and this sector is used as an area extended from the user area. Thus, it can be considered that the sectors following the first sector, i.e., the second sector at an address (track 0100, sector 01) from the leading edge of the spare area and the subsequent sectors are non-assigned areas. As a result the sector at the address (track 0100, sector 01) can be used as an alternative sector of the defective sector detected during recording of data.
As described above, by using both the PDL and the SDL, defects can be handled with respect to all the defective sectors which may be present in the case of the ordinary use of a disk (from disk initialization to data recording and reproduction).
In the above-mentioned method for managing a defect of a disk, a defect is handled only in a sector which is actually determined to have an error in the error determinations E1, E2 (FIG. 14), and E3 (FIG. 16).
However, even a sector which is not determined to have an error may not be accessed. For example, when a scratch causing a tracking error is present in a sector before a target sector (i.e., a sector on which data is to be recorded and from which data is to be reproduced), a track cannot be traced at a time of access. Furthermore, even an address of the target sector may not be read. This is because, considering a rotating disk, the access to the target sector is required to start from a sector before the target sector of a track which cannot be traced. Therefore, an address for accessing the target sector cannot be read, and data cannot be recorded onto or reproduced from the target sector.
FIG. 19 shows a tracking error state in which a head cannot trace a track when trying to access it because of a scratch at an address (track 0011, sector 02) by using a path of the head.
According to a conventional method, as shown in FIG. 20, a sector at the address (track 0011, sector 02) is registered as a defective sector in the PDL or the SDL, and then, a head tries to access a subsequent address (track 0011, sector 03). However, in most cases, the track cannot be traced, resulting in a tracking error. This is because, in order to read data from a sector at the address (track 0011, sector 03), a head is required to access a trailing edge of a sector at the previous address (track 0011, sector 02) at which the head is sidetracked due to a scratch. The head repeats the same movement a couple of times (i.e., the head tries to access the address (track 0011, sector 03). However, a tracking error occurs, making it impossible for the head to access the subsequent sector.
According to the conventional method, in the case where there is a defective sector which prevents a head from tracing a track, only the access to the defective sector is avoided. Therefore, the subsequent sector cannot be accessed.